With ES6 21.2.5.8, step 13, we no longer have to keep up the illusion
that matching and calling replace function is interleaved. This is
observable through unspec'ed static properties such as RegExp.$1.

Last match info not working yet.

R=littledan@chromium.org

Review URL: https://codereview.chromium.org/1418703003

Cr-Commit-Position: refs/heads/master@{#31593}